The present invention relates to antenna mountings and, more particularly, to vehicle antenna mounting structures for mounting antennas on sheet metal mounting surfaces of the vehicle lacking in a great deal of under space between the sheet metal and the interior padding of the vehicle.
There are presently known a number of antenna mounting structures having generally tubular base portions of conducting material. With structure of this type, the antenna is secured within the base and is electrically insulated therefrom. The antenna is connected to the automobile radio by way of a coaxial cable, the inner lead of which is connected to the antenna and the outer lead of which is connected to the base.
A common cable attachment for a tubular-type base antenna is shown in U.S. Pat. No. 2,509,563 to Grashow. In this patent an antenna mounting structure is illustrated which is particularly advantageous in that it may be installed completely from the outside of the mounting surface through a relatively small mounting aperture. When mounted, a portion of the base is disposed beneath the mounting surface and the lower end of the antenna is also beneath the mounting surface, it being disposed within the tubular cavity of the base. A convenient cable attachment is provided in the form of a threaded cap which engages a cooperating threaded portion of the base and also provides electrical contact between the outer lead and the base. The inner lead projects upwardly into the base cavity and is held in contact with the antenna by means of a cooperating pin and plug. Another convenient antenna attachment is shown in U.S. Pat. No. 2,536,053 to Grashow, in which one end of the coaxial cable is provided with a plug adapted to be inserted into the base cavity from below. The inner lead of the cable contacts the antenna by means of a connecting pin projecting from the plug.
Each of the aforementioned cable adaptors provides a simple and expedient means for attaching the cable to the antenna base. This allows the cable and antenna to be sold disassembled and to be attached together just prior to installing the antenna, or to be detached easily, for example, when replacing the antenna.
Connectors of this type, however, are not particularly well suited for installations where the antenna is to be mounted to a mounting surface lacking in a great deal of under space, that is, space between the sheet metal mounting surface and roof padding, since the cable at the connection projects downwardly in the axial direction of the base. In addition, in externally-mountable antennas such as Grashow Pat. No. 2,536,053, the antenna is mounted with the cable already attached and, during one phase of the mounting operation, the antenna base must be lowered through the mounting aperture to a point below where it will be finally secured to the mounting surface (in order to rotate the lower support arms).
Several arrangements are known in the prior art in which an antenna base mounting structure is provided with a cable connection in which the coaxial cable is mounted such that it extends from the mounting structure at a right angle to the axial direction of the base. One such arrangement is shown in U.S. Pat. No. 2,252,671 to Ludwig. In that patent the outer lead of the cable is connected to a ground sleeve by means of a spur, and the inner lead is in electrical contact with the antenna by means of a stud inserted through an aperture in the ground sleeve and insulating sleeve. The use of the ground sleeve and stud increases the time and expense of manufacturing this antenna. Also, the Ludwig antenna is concealed in a sleeve that extends far below the mounting surface, thus making it inappropriate for use where there is limited under space. In fact the right angle connection of Ludwig simply makes it possible to connect a cable to an antenna that is to be stored below a mounting surface and is unrelated to the saving of space.
A more simple arrangement for mounting a cable at a right angle is shown in U.S. Pat. No. 3,145,384 to Nuttle which described an antenna mounting structure that does not extend substantially below the mounting surface. In Nuttle, the coaxial cable is attached to a backing subassembly including a plate having a circular aperture over which a threaded connector jack nipple is welded. The outer lead is connected to this plate and the inner lead extends into the aperture and contacts an inner conductor of the jack. The plate attaches to the bottom of the mounting surface so that the jack extends through a hole in that surface. The antenna screws onto the threads of the jack projecting beyond the mounting surface. The backing subassembly, however, is costly to manufacture and difficult to assemble.